제출 #826023

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
826023		becaido	수천개의 섬 (IOI22_islands)	C++17	0 / 100	1089 ms	9868 KiB

islands

#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("avx,popcnt,sse4,abm")
#include <bits/stdc++.h>
using namespace std;

#ifndef WAIMAI
#include "islands.h"
#endif

#ifdef WAIMAI
#define debug(HEHE...) cout << "[" << #HEHE << "] : ", dout(HEHE)
void dout() {cout << '\n';}
template<typename T, typename...U>
void dout(T t, U...u) {cout << t << (sizeof...(u) ? ", " : ""), dout(u...);}
#else
#define debug(...) 7122
#endif

#define ll long long
#define Waimai ios::sync_with_stdio(false), cin.tie(0)
#define FOR(x,a,b) for (int x = a, I = b; x <= I; x++)
#define pb emplace_back
#define F first
#define S second

const int SIZE = 2e5 + 5;

int n, m;
bool vs[SIZE];
vector<int> ans;
vector<pair<int, int>> adj[SIZE];

int deg[SIZE];
queue<int> q;

int reach() {
    int cnt = 0;
    q.push(0);
    vs[0] = 1;
    while (q.size()) {
        int pos = q.front();
        q.pop();
        cnt++;
        for (auto [np, id] : adj[pos]) if (!vs[np]) {
            vs[np] = 1;
            q.push(np);
        }
    }
    fill(vs, vs + n, 0);
    return cnt;
}

variant<bool, vector<int>> find_journey(int N, int M, vector<int> U, vector<int> V) {
    n = N, m = M;
    for (int i = 0; i < m; i += 2) adj[U[i]].pb(V[i], i);

    int cnt = 0, k = reach();
    FOR (i, 0, n - 1) for (auto [j, id] : adj[i]) deg[j]++;
    if (!deg[0]) q.push(0);
    while (q.size()) {
        int pos = q.front();
        q.pop();
        cnt++;
        for (auto [np, id] : adj[pos]) if (--deg[np] == 0) q.push(np);
    }
    if (cnt == k) return false;

    vector<pair<int, int>> all;
    auto dfs = [&](auto dfs, int pos)->bool {
        vs[pos] = 1;
        for (auto [np, id] : adj[pos]) {
            all.pb(pos, id);
            if (!vs[np]) {
                if (dfs(dfs, np)) return 1;
                all.pop_back();
                continue;
            }
            int l, r = all.size() - 1;
            FOR (j, 0, r) if (all[j].F == np) {
                l = j;
                break;
            }
            FOR (j, 0, l - 1) ans.pb(all[j].S);
            FOR (j, l, r) ans.pb(all[j].S);
            FOR (j, l, r) ans.pb(all[j].S ^ 1);
            for (int j = r; j >= l; j--) ans.pb(all[j].S);
            for (int j = r; j >= l; j--) ans.pb(all[j].S ^ 1);
            for (int j = l - 1; j >= 0; j--) ans.pb(all[j].S);
            return 1;
        }
        vs[pos] = 0;
        return 0;
    };
    if (dfs(dfs, 0) == 0) return false;
    return ans;
}

/*
in1
4 5
0 1
1 2
2 3
0 3
3 1
out1
1
10
0 1 2 4 0 3 2 1 4 3

in2
2 3
0 1
1 0
1 0
out2
0
0
*/

#ifdef WAIMAI
int main() {
  int N, M;
  assert(2 == scanf("%d %d", &N, &M));

  vector<int> U(M), V(M);
  for (int i = 0; i < M; ++i) {
    assert(2 == scanf("%d %d", &U[i], &V[i]));
  }

  variant<bool, vector<int>> result = find_journey(N, M, U, V);
  if (result.index() == 0) {
    printf("0\n");
    if (get<bool>(result)) {
      printf("1\n");
    } else {
      printf("0\n");
    }
  } else {
    printf("1\n");
    vector<int> &canoes = get<vector<int>>(result);
    printf("%d\n", static_cast<int>(canoes.size()));
    for (int i = 0; i < static_cast<int>(canoes.size()); ++i) {
      if (i > 0) {
        printf(" ");
      }
      printf("%d", canoes[i]);
    }
    printf("\n");
  }
  return 0;
}
#endif

컴파일 시 표준 에러 (stderr) 메시지

islands.cpp: In lambda function:
islands.cpp:88:35: warning: 'l' may be used uninitialized in this function [-Wmaybe-uninitialized]
   88 |             for (int j = l - 1; j >= 0; j--) ans.pb(all[j].S);
      |                                 ~~^~~~
islands.cpp:87:31: warning: 'l' may be used uninitialized in this function [-Wmaybe-uninitialized]
   87 |             for (int j = r; j >= l; j--) ans.pb(all[j].S ^ 1);
      |                             ~~^~~~
islands.cpp: In function 'std::variant<bool, std::vector<int, std::allocator<int> > > find_journey(int, int, std::vector<int>, std::vector<int>)':
islands.cpp:88:22: warning: 'l' may be used uninitialized in this function [-Wmaybe-uninitialized]
   88 |             for (int j = l - 1; j >= 0; j--) ans.pb(all[j].S);
      |                      ^

• Subtask 1: 0 / 5
• Subtask 2: 0 / 5
• Subtask 3: 0 / 21
• Subtask 4: 0 / 24
• Subtask 5: 0 / 45